Using Frame API for C, Need to change Data size for a TX Object

[Genesis]

I need to Transmit different messages to the same ArbitrationID address. The Transmited messages have variable lengths. Can I call ncConfig on an object to change the NC_ATTR_CAN_DATA_LENGTH even after the call to ncOpenObject. Or do I have to Close the object and reopen it after the call to ncConfig?

Thanks!

[biker2000]

Hello Genesis,

your second assumption is right. You do have to close, reconfigure and reopen the object in order to change the data length.
As long as you're using the CAN Object in the 'Transmit Data by Call' mode only, you might want to consider using the Network Interface for transmitting. When you use the Network Interface, you can change the ArbitrationID for each write call.

-B2k

[Genesis]

Is the Network Interface another API. Where is the documentation for this API?
Thanks for you response!

[biker2000]

The 'Network Interface Object' is part of the Frame API. You can think of it as a port-level access whereas the 'CAN Object' one layer down and it only allows to work with a particular ArbitrationID (specified in its configuration).
Take a look at the NI-CAN Hardware and Software Manual. Chapter 9 (Using the Frame API) discusses the use cases of both object types.